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Questions tagged [seismology]

For questions about the study of earthquakes and various seismic sources.

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8 votes
2 answers
3k views

Distance to epicenter vs distance to focus

I am not really a "budding seismologist." I am a chemistry/physics teacher teaching an Earth science class (low academic level) in a small-town high school. (My college coursework in earth sciences = ...
Darwin Smith's user avatar
18 votes
2 answers
2k views

Why Vp/Vs and not Vs/Vp?

The relation between shear wave velocity (Vs) and pressure wave velocity (Vp) is often expressed as Vp/Vs. Wouldn't the opposite be more logic? Vs/Vp would never lead to division with zero and the ...
user2821's user avatar
  • 5,946
6 votes
1 answer
425 views

Earthquake probabilities

A recent report estimated the probability of an earthquake greater than magnitude 7 on the southern section of the San Andreas fault at approximately 60% over the next thirty years. How is that ...
Daijohn's user avatar
  • 63
8 votes
1 answer
4k views

Calculating the displacement of a fault

In the calculation of scalar moment magnitude of an earthquake we have the formula $$M_0=\mu AD$$ where: $\mu$ is the shear modulus of the rocks involved in the earthquake (in Pa) $A$ is the area ...
shrey's user avatar
  • 1,489
17 votes
2 answers
433 views

How strong can a glacial icequake get?

While researching Antarctic geology, I came across the term 'icequake' in the abstract to the article Seismicity within a propagating ice shelf rift: The relationship between icequake locations and ...
user avatar
8 votes
1 answer
249 views

About Earthquakes and their properties

I know this sounds like a crazy observation but San Francisco has a lot of HUGE buildings in the downtown area , millions of tons or probably more. Many Scientists think a big earthquake there is '...
201044's user avatar
  • 587
15 votes
3 answers
5k views

Do other terrestrial planets have "earthquakes"?

I know some planets have storms akin to what we have on Earth although obviously varying in nature. I was wondering if other planets have earthquakes? Since this comes down to plate tectonics (right?...
Stan Shunpike's user avatar
12 votes
4 answers
3k views

What do the derivative or the integral of amplitude of a seismogram mean?

I'm doing a project in which I'm analyzing earthquake seismogram waves. I used a program to graph the exact amplitudes and how they changed over the course of a single earthquake. For the project I ...
Neeeedhelp's user avatar
14 votes
1 answer
212 views

How are Richter magnitudes of past earthquakes estimated?

In reading about historical major earthquakes, in particular, the Great Shaanxi Earthquake that killed approximately 830,000 people in July, 1556, there is a claim made about the approximate Richter ...
user avatar
12 votes
1 answer
240 views

Why does seismic activity shed light on the inner core rigidity?

Reading Introduction to Geology (MIT 2005) and Wikipedia's article on Earth's inner core, it is specified that: Earth was discovered to have a solid inner core distinct from its liquid outer ...
Chirac's user avatar
  • 924
12 votes
1 answer
2k views

converting SU file to ASCII format in seismic unix using OpenSeaSeis

I have tried to convert a Seismic SU file to ASCII format in seismic unix using openseaseis module named "sutoascii". I have already tested the SU file by opening it in SeaView Seismic Viewer and ...
abhinavgoyal02's user avatar
14 votes
1 answer
726 views

Successful Earthquake predictions

Have there been any instances where seismologists have successfully predicted the occurrence of earthquakes? If so, then why has the number of scientists working on this area has declined (as ...
shrey's user avatar
  • 1,489
12 votes
2 answers
1k views

Temporal Resolution of Seismic data

Radius of the Fresnel zone is given by $$Rf=(v/2)(t_0/f_\mathrm{dom})^{1/2}$$ where $v$: velocity of layer $t_0$: two way travel time $f_\mathrm{dom}$ :dominant frequency in the spectrum This shows ...
shrey's user avatar
  • 1,489
16 votes
1 answer
522 views

How much silicon is in the Earth's core, and how did it get there?

With some informal conversation with a peer of mine, he had suggested that there is evidence (which he couldn't find,but had remembered reading) that there was Silicon in the Earth's core. I referred ...
Neo's user avatar
  • 6,456
13 votes
2 answers
417 views

How accurately can explosions be triangulated from the IRIS seismogram data?

There's a bunch of armed conflicts going on right now. What are the lower boundaries on accuracy of triangulating and timing man-made events from the IRIS datasets (accessible, for instance, with the ...
Deer Hunter's user avatar
  • 2,103
12 votes
1 answer
582 views

Where and how can seismic data for earthquakes and volcanoes be downloaded?

I need it in this format. I went to USGS and IRIS websites but couldn't understand the downloading procedure
shrey's user avatar
  • 1,489
11 votes
1 answer
181 views

What efforts have been made to separate the microseismic events related to wind-related ocean waves from the components of volcanic origin?

I have read the question What generates the microseism? and it's accompanying answer. In [#1, cited below], they use the azimuth values of seismographic activity on the flanks of the volcano ...
jonsca's user avatar
  • 1,079
9 votes
1 answer
169 views

What are the factors that dictate a given topology for seismometer placement around a volcano?

The image below (borrowed from [#1]) shows the topology of the seismometers around the volcano Stromboli. In the text, they explain the following: The seimometers were set on the flanks of the ...
jonsca's user avatar
  • 1,079
15 votes
1 answer
2k views

Interpretation of a seismogram (three components)

In most cases (as shown in the figure below), a seismogram shows data from three components: North-South East-West Vertical/depth(z) However, if these components are not marked and all we have are ...
shrey's user avatar
  • 1,489
14 votes
1 answer
2k views

Why are there more intense earthquakes in Iran than in Iraq?

Why are there more intense earthquakes in Iran than in Iraq, if they are so close together? I often hear news items of earthquakes in Iran that are higher on the Richter Scale than those that happen ...
Reuven's user avatar
  • 341
13 votes
1 answer
247 views

Epicenter location of the 900-930 A.D.,7.4 Magnitude Seattle Earthquake?

I am preparing a seismic hazard map of Seattle and I was curious about the great 7.4 magnitude earthquake that occurred in the Seattle area during 900-930 A.D. On a second note, is it possible to ...
Guru Rahul Pradhan's user avatar
17 votes
1 answer
501 views

Can earthquakes contribute to Antarctic ice loss?

I read about the earthquake that took place in Japan in 2011, led to some small calving events in Antarctica (link). So, it makes me think if there is a big earthquake near or in Antarctica, can it ...
Vikram's user avatar
  • 785
11 votes
1 answer
354 views

Relation between fault rupture aspect ratio and slip rate?

I am modeling a fault surface (which I consider to be a plane rectangle). I got the area of the surface, but the orientation is unknown, which can be found out if the aspect ratio of the rectangle is ...
user590's user avatar
  • 361
12 votes
1 answer
222 views

Probability distribution of fault throw displacement and height limiting mechanisms

First, what is the probability distribution of fault throw displacement. Uniform distribution seems unlikely, since then small changes would add up to huge huge elevation differences that require a ...
user877329's user avatar
13 votes
1 answer
7k views

P wave to S wave conversion

While passing through layers inside the earth some P waves get converted to S waves and then back to P waves while returning towards the surface. Is this statement true? If yes, then why? (...
shrey's user avatar
  • 131
15 votes
0 answers
168 views

What are the ground motion prediction equations for 3-D ruptures?

Ground motion prediction equations (GMPEs) estimate ground motion at any given site due to an earthquake at a distance. There are many such equations, each with different parameters. Can somebody ...
user590's user avatar
  • 361
12 votes
1 answer
742 views

What causes "shallow" moonquakes?

It is thought that "deep" moonquakes are caused by tidal forces exerted on the Moon by the Earth and Sun. Some other sorts of moonquakes are thought to be caused by impacts, or by thermal expansion (...
senshin's user avatar
  • 1,885
14 votes
2 answers
4k views

Why is colored seismic inversion called 'colored'?

One of the seismic inversion algorithms is called 'colored' inversion. It is performed in the frequency domain and the point is in building an operator that directly transforms a seismic trace into ...
antongrin's user avatar
  • 315
13 votes
1 answer
3k views

Is there any correlation between La Niña/El Niño and seismic activity?

I've read in the past that extreme precipitation levels may have an effect on seismic activity, and wondered if anyone has ever analysed the La Niña / El Niño cycles to see if there is any correlation ...
db9dreamer's user avatar
19 votes
1 answer
576 views

What are the physical upper bounds on the magnitude of an earthquake?

Given what we know about the physical mechanisms underlying earthquakes, what do the theoretical upper bounds on the magnitude of an earthquake look like? What physical phenomena impose those upper ...
senshin's user avatar
  • 1,885
22 votes
3 answers
737 views

Are there any techniques for imaging the deep Earth besides seismic waves?

It is well-known that we can learn a lot about the structure of the lower crust, mantle, and core by observing the ways in which they refract different kinds of seismic waves. Do we have any other ...
senshin's user avatar
  • 1,885
32 votes
8 answers
3k views

Is earthquake prediction possible?

After the Tohoku and East Coast quakes, I skimmed over several books discussing the validity of earthquake prediction as a discipline, yet found no significant breakthroughs. What should change in our ...
Deer Hunter's user avatar
  • 2,103
44 votes
6 answers
108k views

Are Richter-magnitude 10 earthquakes possible?

The largest earthquake since 1900 according to the United States Geological Survey (USGS) was Richter-9.5 magnitude quake in Chile in 1960. Are magnitude 10 earthquakes possible? If so, what is the ...
blunders's user avatar
  • 4,611
12 votes
1 answer
272 views

Do seismic travel times from one location to another differ based on factors other than distance?

Bit puzzled why it appears that seismic travel times from one location to another appears to just be a function of the distance, and not any other factors. Do seismic travel times from one location ...
blunders's user avatar
  • 4,611
20 votes
2 answers
48k views

How do seismologists locate the epicenter and focus of an earthquake?

I know the focus of an earthquake is where the earthquake originated from, but what I could never figure out is, how to scientists find out where exactly the focus (and epicenter) are located?
Azzie Rogers's user avatar
  • 2,842
21 votes
4 answers
2k views

What would a replacement for SEGY look like?

I have been having a miserable time this week reading SEGY files. This is data from the largest seismic acquisition company in the world whose client is the 7th largest oil company in the world. So if ...
Candid Lunch's user avatar
12 votes
1 answer
241 views

Do normal modes of oscillation cause permanent deformation?

It is known that when a large earthquake occurs, say $M \ge 9.0$, The surface waves travel around Earth over and over, "ringing the surface like a bell". The GIF below is an example (Image Source): ...
Neo's user avatar
  • 6,456
9 votes
2 answers
444 views

Is seismology really the only way to measure the thickness of Earth's layers?

Answers from these two questions: How can we guess the size of the earths inner core? & How can we measure the thickness of the earths mantle? use seismic waves as the method for detirmining ...
Ben A. Noone's user avatar
  • 1,524
35 votes
4 answers
16k views

How can we determine the size and composition of Earth's inner core?

From Wikipedia: Earth's inner core is Earth's innermost part and is a primarily solid ball with a radius of about 1,220 km (760 mi). (This is about 70% of the Moon's radius.) It is believed to consist ...
Ben A. Noone's user avatar
  • 1,524
11 votes
1 answer
181 views

How do we determine subsurface composition?

Let's assume that a seismogram $s(t)$ is the convolution $s(t)=r(t)g(t)$ between a source signal $r(t)$ and propagation effects $g(t)$. If the source signal $r(t)$ is known, then we can obtain the ...
Paul's user avatar
  • 1,151
14 votes
2 answers
730 views

Why is a seismogram interpreted as a convolution?

I remember reading in a geology book that a seismogram is a convolution between a source signal and propagation effects. In layman's terms, what does this really mean?
Paul's user avatar
  • 1,151
23 votes
3 answers
12k views

How to distinguish P, S, Love, and Rayleigh waves in a seismogram?

What features should I look for to determine each of these kinds of waves in a seismogram? What signal processing methods (filters, transforms, etc...) should I use to determine them?
Paul's user avatar
  • 1,151
14 votes
2 answers
398 views

How are subsurface wave speeds determined without subsurface sensors?

This is something I've never quite understood from a geology class I took years ago: Consider the following picture (courtesy of wikipedia) Obviously, we can't possibly have sensors deep in the ...
Paul's user avatar
  • 1,151
22 votes
1 answer
153 views

Placement of crustal thickness estimation from 1D inversion of surface wave dispersion curves

Seismic surface waves present a characteristic dispersion behavior in which different frequencies travel at different speeds. This characteristic dispersion curve depends on the shear and ...
Leo Uieda's user avatar
  • 883
12 votes
2 answers
685 views

What determines the spectrum of high and low frequency waves emitted by an earthquake?

Does the shape of the fault that the earthquake originated from determine its ratio of high frequency to low frequency waves? What about shallow-fault vs deep subduction zone earthquakes?
InquilineKea's user avatar
  • 7,827
11 votes
1 answer
706 views

What generates the microseism?

Looking at seismic noise around the Earth there is commonly a peak in the seismic noise around a frequency of 200 mHz. This peak is typically referred to as the microseism (an example is shown below)....
Chris Mueller's user avatar
22 votes
3 answers
444 views

Is fracking likely to produce earthquakes?

Post Christchurch-2011 earthquake, there was much concern that fracking in the surrounding areas might lead to further quakes, as was rumoured to have happened elsewhere in the world. Is there ...
Mark Mayo's user avatar
  • 848
20 votes
2 answers
939 views

How does one measure what causes earthquakes?

I know that they occur when energy that was previously stored is released in seismic waves. But how is the energy stored in the earth in the first place, and what can trigger the release of such ...
Tom Au's user avatar
  • 2,244

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